SUGARBEET YIELD AND QUALITY IN A
POTATO-SUGARBEET ROTATION
(Preliminary Results)

Lance J. Reitmeier – M. S. Candidate, NDSU, Fargo, ND
David W. Franzen – Extension Soil Specialist, NDSU, Fargo, ND
Joseph F. Giles – Associate Professor, NDSU, Fargo, ND
Allan Cattanach – Sugarbeet Specialist, NDSU/U of MN, Fargo, ND
Norman R. Cattanach – Research Specialist, NDSU, Fargo, ND

Potato and sugarbeet quality is greatly influenced by the amount of nitrogen present in the soil. A four-township area near St. Thomas, ND has been facing significant economic losses due to continuous low beet quality, i.e., low sugar content and high sugar loss to molasses. Five years of compiled data have suggested that excess nitrogen still available at harvest may be the primary cause.

It was decided that the project be conducted using a site-specific approach rather than using a restricted research plot approach. Justification for this approach is due to the apparent "full-field" problem and not a small area of concern.

Objectives:

  1. Determine the relationship between high field nitrate-N levels and sugarbeet yield and quality.
  1. Determine the effect of variable-rate N applications on sugarbeet and potato yield and quality (conventional vs. grid vs. topography zone applications).

Procedures:

Sugarbeet Research

Two fields in sections 34 and 29 of St. Thomas S. Township, ND, to be sugarbeets in 1997, were divided into three-acre grids and soil sampled to a depth of 4’ in the fall of 1996. These fields had both conventional and variable rate nitrogen applications randomly applied to all of the grids. Field #1 (38 acres) had a conventional nitrogen recommendation of 36 lbs. N/acre, Table 1, and field #2 (50 acres) had a conventional nitrogen recommendation of 69 lbs. N/acre, Table 2.

Each of the sugarbeet fields was divided into acre (150’ x 150’) grids on July 1 and July 7, 1997. Coordinates for each of these grids was recorded with a backpack GPS unit on August 14. Within each of these grids, two 10’ rows were thinned to a population of 150 beets/100’ of row. The strips were to be used for yield and quality data and also for nitrogen content and dry matter yield of the tops.

Four petiole samples were taken from each acre grid on both fields July 22, August 8, August 20, and September 4. Approximately 25-30 petioles were taken in a diamond shape at each grid. The samples will be analyzed for nitrate-N content and variability.

Aerial photographs were taken by AGSCO of Grand Forks, ND on August 4, 11, 27, and September 5 of field #1. Aerial photographs were taken of field #2 on July 28, August 11, 27, and September 5. Satellite images were also taken for both fields on July 16, August 2, and August 26. The photographs and images are to be layered over the petiole nitrate-N maps, yield maps (figures 1 and 4), and sucrose maps (figures 2 and 5).

The strips were hand harvested on both fields from each grid on September 18. Tops were weighed in the field and sub-samples were taken for determination of dry matter and total nitrogen content. The sugarbeets were analyzed for quality at the American Crystal tare lab in East Grand Forks, MN.

Soil samples were taken on field #1 and #2 on October 23 and October 30, respectively. The samples were taken in each acre grid at depths of 0-6", 6-24", 24-48", and 48-72". Soil analysis is currently being performed at the NDSU soil-testing lab.

Potato Research

Two forty-acre potato fields were located in section 34 and 29 of St. Thomas S. Township, ND. These fields were split into acre grids (150’ x 150’) on July 29, 1997. Coordinates for each of these grids were recorded on August 14 with the use of a backpack GPS unit. These fields will be planted to sugarbeets in the spring of 1998.

Twenty-five petiole samples were taken from each grid on of potato field A and all of potato field B on July 29. Petiole samples were taken from the other of potato field #1 on July 31. These samples will be analyzed for nitrate-N content and variability within the field.

Aerial photographs, taken by AGSCO of Grand Forks, ND, were shot on August 4, 11, 27, and September 5 on field A. Aerial photographs of field B were taken on July 28, August 11, 27, and September 5. Satellite images of both fields were also taken on July 16, August 2, and August 26. They will be layered over the petiole maps, dry matter yield maps, and soil nitrogen maps which have not yet been constructed.

Potato vine samples were taken from 10’ of row on August 28. These samples were weighed in the field and a sub-sample was taken to analyze dry matter content and total nitrogen content.

Soil samples of fields A and B were taken on October 16. Samples at 0-6", 6-24", 24-48", and 48-72" were taken from each grid. These samples are currently being analyzed at the NDSU soil-testing lab. Simplot out of Grand Forks, ND has also made topography maps of both of these fields. These maps will be used to adjust fertilizer recommendations accordingly by topographic zones.

Results and Discussion:

Quality analysis of each of the two sugarbeet fields showed an advantage of $24.64 gross return/acre overall. Table 3 and Table 4 compare the effects of conventional vs. variable rate applications on the yield and quality of the sugarbeets.

Soil test nitrogen recommendations on field #1 showed a need for 55 lbs. more nitrogen with the variable rate method than the conventional method. On Field #2, nitrogen recommendations called for 8 lbs. less nitrogen from variable rate application than conventional fertilizer recommendation methods. The soil test recommendations, based on 4’ depths, do not take into account the possibility of nitrogen extraction by the sugarbeets deeper than 4’.

It has been predicted that there is a significant amount of deep nitrogen that is accounting for historically low quality in the St. Thomas, ND area. If this is the case, even a nitrogen recommendation of 0 lbs./acre may result in poor quality sugarbeets. Perhaps nitrogen levels have been built up quite high and a few years may be needed to deplete these levels. If this is the case, variable rate nitrogen applications may be more appropriate as to prevent continuous over-fertilization.

Maps illustrating the variability of yield, sucrose content, and recoverable sugar/acre have been constructed for both field #1, Figure 1, and field #2, Figure 2. Relationships between nitrogen content, root yield, and sucrose content are to be determined once all of the data results are processed.

Preliminary results have pointed to 2 distinct areas in sugarbeet field #1 where a relationship between nitrogen, yield, and sucrose content is being illustrated. An area in the southwest corner (bottom left-hand corner) is showing signs of excess soil nitrogen levels. Yields in this corner are averaging over 22 tons/acre and sucrose contents are down in the 14% to 15% range.

Another area towards the eastern end (right-hand side) of this same field is also showing definite relationships between nitrogen, yield, and sucrose content. Although, what is being seen in this area are both low yields and low sucrose contents. Preliminary assumptions are that there are excess nitrogen levels in this area also, and yields are being affected by another factor such as low plant populations, disease influences, or presumably something else that is not known at this time.

The recoverable sugar/acre map for this field illustrates these areas quite prominently also. Both the areas of high yield and low yield seem to be averaging similar lbs./acre recoverable sugar due to the low sucrose contents. The additional tons are not significantly increasing the recoverable sugar/acre compared to the area with lower yields.

Field #2 also has areas that show a distinct relationship between nitrogen, root yield, and sucrose content. An area near the east-southeast (top right-hand corner) side of this field is illustrating yields ranging on an average from 26 to 28+ tons/acre. The sucrose contents of this same area are averaging around 15% to 16%. Similarly, an area on the west-northwest (bottom left-hand side of the map) side of this field is showing yields again in the 26 to 28+ tons/acre range. These areas are both showing signs of excess soil nitrogen still available at harvest.

Gross return/acre has been mapped out in Figure 3 for both of these fields. On the first field the results of low sucrose contents are obvious. Both areas that were pointed out are showing significant losses in gross return/acre. The second field is not quite so obvious as to the relationships between the nitrogen, yield, and sucrose content. High root yields have made up for the lack of sucrose content as illustrated by the gross return/acre.

Some preliminary results of soil tests can be seen in Figure 4. These nitrogen levels are from approximately a 10-acre area in potato field A. These maps, illustrating nitrogen levels from 0 to 6’, are showing high levels of nitrogen and a definite relationship between these levels within the soil profile.

Soil nitrogen tests down to 4’ are suggesting that approximately of this 10-acre area is already beyond nitrogen recommendations for sugarbeet production. Soil test nitrogen levels are also illustrating anywhere from about 50 to 100 lbs. more nitrogen in the additional 2’ below the 4’ levels. These nitrogen levels below 4’ could very likely be available to extraction by the 1998 sugarbeet crop towards the later part of the growing season.

Assumptions should not be made as to the quality of the 1998 sugarbeet crop on such a small section of this field. If this 10-acre area is representative of the rest of this field, these high nitrogen levels should be detrimental to the quality of the 1998 crop.

It has also been suggested that potato vines and culls left in the field may be adding a significant amount of nitrogen, available to the following sugarbeet crop, that has not yet mineralized at the time of soil sampling. Further analysis of data may support this hypothesis.

As of this report, nitrogen analysis on the potato vines and sugarbeet tops have not yet been determined. The nitrate-N content of the petiole samples and soil test results have likewise not yet been determined and therefore relationships cannot be suggested at this point.

The 1998 report on data analysis should be more conclusive.

Acknowledgments:

Partial Funding - American Crystal Sugar Company, Moorhead, MN
- Sugarbeet Research and Education Board of Minnesota and North Dakota
Cooperator - Pete Carson, St. Thomas, ND Grower
Aerial Photography - AGSCO
Topography Maps - Simplot
Data Collection - Dave Hilde, American Crystal Sugar Company
Quality Analysis - American Crystal Sugar Company Tare Lab, East Grand Forks, MN

1997 Sugarbeet Research and Extension Reports. Volume 28, pages 159-166


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